A problem with existing systems is that in some agricultural vehicles, especially tractors, each vehicle has a unique access key for locking and un-locking the cab doors. However, many similar vehicles then use the same mechanical ignition key to start the engine and permit operation of the tractor. This is done for convenience to enable employees on a farm to use a common key to operate any vehicle once its cab has been unlocked by the farmer.
One way to address this concern is to provide the key with a specific code to identify itself to the unit in order to allow access to the vehicle functions. Such keys need to be programmed to allow access and there is a concern that it may be possible for a third party to access identifying information from the CAN bus whilst programming. Additionally, it is desirable for an ECU of the vehicle to be interrogated, for example to retrieve maintenance and log information, without third parties being able to intercept the information being transferred.